1. Field of the Invention
The present invention relates to battery chargers, and more particularly to a method of estimating recharging time of a rechargeable battery and a related charging device.
2. Description of the Prior Art
Batteries are a class of power supplies that are self-contained, and usually portable. Batteries use electrochemical reactions to generate electricity from a variety of chemicals. Rechargeable batteries are batteries whose electrochemical reaction can be reversed electrically to restore the rechargeable battery to a state wherein the electrochemical reaction can be performed again to generate electricity. Typical rechargeable batteries may be recharged for a number of cycles in the hundreds to thousands. Rechargeable batteries are employed in a wide variety of electronic consumer products, especially portable electronic devices, such as cellular phones, multimedia devices, and notebook or netbook computers.
To take advantage of processing and display functions of the portable electronic devices, a Smart Battery System (SBS) has been proposed that allows operating systems to communicate with the rechargeable battery through a data bus, such as a System Management Bus (SMBus). The operating system may receive SBS parameters, such as Average Time To Full (ATTF), from the rechargeable battery, and may display the parameters in a graphical user interface to inform a user of the portable electronic device of battery status. The operating system may also control power management functions of the rechargeable battery through the SMBus.
Please refer to FIG. 1, which is a block diagram of a battery device 10 according to the prior art. The battery device 10 may be installed in a housing, and may be electrically connected to a notebook computer for powering internal circuits and electrical devices, such as a hard disk drive and a liquid crystal display (LCD), of the notebook computer. The battery device 10 may comprise a plurality of battery cells 100, a battery management integrated circuit (IC) 110, and a notebook charger connector 120 installed in the housing. The notebook charger connector 120 may be electrically connected to a positive terminal (+) and a negative terminal (−) of the plurality of battery cells 100. The notebook charger connector 120 may be electrically connected to the positive terminal of the plurality of battery cells 100 through a fuse 130 and a switch 140, and may be electrically connected to the negative terminal of the plurality of battery cells 100 through a current sensing resistor 150. Gas gauge and status messages, as well as control signals, may be transferred between the battery management IC 110 and the notebook charger connector 120 through a System Management Bus (SMBus) 160. The plurality of battery cells 100 may provide direct current (DC) power to the notebook computer at a voltage level ranging from 16 Volts to 18 Volts, though higher or lower voltages may also provided by the plurality of battery cells 100 for powering the notebook computer. The plurality of battery cells 100 may be arranged in any combination of series and parallel connections. For example, as shown in FIG. 1, the plurality of battery cells 100 may comprise four individual battery cells arranged in series. The battery management IC 110 may control the fuse 130 and the switch 140 for preventing overcurrent and/or overvoltage events from damaging the notebook computer. The switch 140 may be a transistor having a control terminal electrically connected to the battery management IC 110. The battery management IC 110 may also be electrically connected to first and second terminals of the current sensing resistor 150 for detecting the overcurrent event. The battery management IC 110 may have a terminal electrically connected to a thermistor 190 for regulating output of the DC power in response to temperature variations detected through the thermistor 190. The battery management IC 110 may also control a plurality of light-emitting diodes (LEDs) 195 for providing battery status messages to a user of the notebook computer. The plurality of LEDs 195 may be visible through the housing.
While the SBS provides greater flow of information between the operating system and the rechargeable battery, the user may have a difficult time accurately predicting remaining time to full charge from the ATTF parameter. ATTF is typically calculated as (Full Charge Capacity−Remaining Capacity)/(Average Current). However, this method of calculating ATTF is inaccurate. Further, the user is not provided with useful data for informing the adoption of a recharging settings strategy. Finally, the recharging settings cannot be optimized automatically.